In order to meet large quantity and short delivery time printing requirements from customers, in recent years sheet feeding apparatuses that continuously supply large quantities of sheets at a high speed, or image forming systems in which image forming apparatuses and said sheet feeding apparatuses are connected have become necessary.
As a sheet feeding apparatus of this type, apparatuses have been known that are provided with a flotation section that causes the upper part of the sheets stacked in a stacking section to float, a separating section that separates the sheets that have been floated by the flotation section, and a sheet conveying section of the belt type that conveys a sheet that has been separated by the separating section while sucking it.
In concrete terms, the flotation section and the separating section use nozzles for flotation and nozzles for separation provided on a single air flow duct;
by blowing air from the nozzle for floating at the end part of the sheets stacked in the stacking section, and by causing air to flow between sheets, causes a plurality of sheets to float, by blowing air from the nozzle for separation on the side of the conveying section, and the air repelled from the conveying section is made to come in contact with the floated sheets thereby separating them;
by providing a suction box inside a belt passed over a pair of rollers, causing a negative pressure inside the suction box, a sheet is conveyed while sucking and holding it (see, for example, Patent Document 1).
Further, sheet feeding apparatuses are known (see, for example, Patent Document 2) that have nozzles for flotation and nozzles for separation provided on a single air flow duct; and that,
using an ON/OFF mechanism that turns ON/OFF the fan that blows air to the single air flow duct, and by turning ON/OFF the air that is ejected from the nozzle for flotation and the nozzle for separation at prescribed timings, carry out sheet flotation and sheet separation.
Further, even the size and type (for example, grammage) of the required output sheet are varied, for example from A3 size to post card size, grammage of 300 g/m2 to 60 g/m2, and generally it is known that sheets of a small size and small grammage can easily flutter at the time of picking up the sheet.    Patent Document 1: Unexamined Japanese Patent Application Publication No. 2002-2986.    Patent Document 2: Unexamined Japanese Patent Application Publication No. 2005-162419.